The halide shown is heated with sodium ethoxide in ethanol. Which structure is the major alkene formed?

The halide is 2-bromopentane and a small unhindered ethoxide follows the Saytzeff rule, removing a beta-hydrogen from C-3 to give the more substituted pent-2-ene. The trans (E) isomer is more stable than the cis (Z), so it predominates. Pent-1-ene is minor and the ether is the minor SN2 product.